The emergence and augmentation of the frequency of resistance of Plasmodium falciparum to SP, which has already been observed in numerous countries of sub-Saharan Africa and in the Central African Republic, challenges the short-term usefulness of this drug combination in the prevention of malaria in pregnant women. The resistance is due to accumulation of point mutations at various sites on the genes coding for dihydrofolate reductase (dhfr) and dihydropteroate synthase (dhps). The number of mutations correlates with the extent of resistance of Plasmodium falciparum to SP in vitro. In studies carried out in Bangui, the prevalence of therapeutic failure was estimated to be 23.8% after 14 days of follow-up among children with uncomplicated malaria, while the resistance of Plasmodium falciparum to pyrimethamine in vitro was reported to be 38.3%. The frequency of mutations in dhfr and dhps alleles is correlated with in vitro response of Plasmodium falciparum strains to SP.